Semiconductor device

ABSTRACT

A semiconductor device is disclosed. The semiconductor device has a semiconductor chip, an island having an upper surface to which the semiconductor chip is bonded, a lead disposed around the island, a bonding wire extended between the surface of the semiconductor chip and the upper surface of the lead, and a resin package sealing the semiconductor chip, the island, the lead, and the bonding wire, while the lower surface of the island and the lower surface of the lead are exposed on the rear surface of the resin package, and the lead is provided with a recess concaved from the lower surface side and opened on a side surface thereof.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 13/930,670,filed on Jun. 28, 2013, which was a divisional of application Ser. No.13/141,222, filed on Sep. 1, 2011, now U.S. Pat. No. 8,502,359.Furthermore, this application claims the benefit of priority of Japaneseapplication 2008-326113, filed Dec. 22, 2008. The disclosures of theseprior U.S. and Japanese applications are incorporated herein byreference.

TECHNICAL FIELD

The present invention relates to a surface-mounted semiconductor device.

BACKGROUND TECHNIQUE

The so-called non-leaded package eliminating extension of leads from aresin package and exposing the leads (outer leads) on the lower surfaceof the resin package is known as a surface mount package.

A semiconductor device employing the non-leaded package has a structureobtained by sealing a semiconductor chip with a resin package along witha lead frame. The lead frame is formed by punching a thin metal plate,and includes an island and a plurality of leads arranged around theisland. The semiconductor chip is die-bonded to the upper surface of theisland, and electrically connected with each lead by a bonding wireextended between the surface thereof and the upper surface of each lead.The lower surfaces of the island and each lead are exposed on the rearsurface of the resin package.

PRIOR ART Patent Document

Patent Document 1: Japanese Unexamined Patent Publication No. 2007-95788

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In such a structure, each lead is held in the resin package only bybonding power between the upper surface and side surfaces thereof andthe resin package. Therefore, the lead may come off the resin package.

Accordingly, an object of the present invention is to provide asurface-mounted semiconductor device capable of attaining improvement inbonding strength between a lead and a resin package.

Means for Solving the Problem

A semiconductor device according to the present invention for attainingthe aforementioned object includes a semiconductor chip, an islandhaving an upper surface to which the semiconductor chip is bonded, alead arranged around the island, a bonding wire extended between thesurface of the semiconductor chip and the upper surface of the lead, anda resin package collectively sealing the semiconductor chip, the island,the lead and the bonding wire, while the lower surface of the island andthe lower surface of the lead are exposed on the rear surface of theresin package, and the lead is provided with a recess concaved from thelower surface side and opened on a side surface thereof.

In the semiconductor device, the lower surfaces of the island to whichthe semiconductor chip is bonded (die-bonded) and the lead electricallyconnected with the semiconductor chip by the bonding wire are exposed onthe rear surface of the resin package collectively sealing the same.Therefore, the semiconductor device is surface-mountable on a wiringboard.

The lead is provided with the recess concaved from the lower surfaceside thereof and opened on the side surface. The material for the resinpackage infiltrates into the recess, whereby part of a peripheral edgeportion of the lead is held by the resin package from both of the upperand lower sides thereof. Thus, improvement in bonding strength betweenthe lead and the resin package can be attained. Consequently, the leadcan be prevented from coming off the resin package.

Preferably, the recess has a portion arcuately shaped in bottom planview. According to this structure, the bonding strength between the leadand the resin package in all radial directions of the arcuate shape canbe increased.

When, in a case of such a structure that a side surface of the lead isexposed on a side surface of the resin package, the recess is formed tobe opened on the exposed side surface, for example, it is apprehendedthat the recess is blocked by a molding die for formation of the resinpackage and the material for the resin package does not infiltrate intothe recess.

Therefore, the recess is preferably opened on a side surface of the leadopposed to the island. Thus, the recess is not blocked by the moldingdie and hence the material for the resin package can be reliablyinfiltrated into the recess, whereby the bonding strength between thelead and the resin package can be reliably improved.

The island may be quadrangularly shaped in bottom plan view, and thelead may be arranged on a portion opposed to each of four sides of theisland in plan view, and provided in a shape having a side parallel tothe opposed side. In this case, the recess is preferably opened on aside surface of each lead having a side opposed to each side of theisland. Thus, the material for the resin package can be reliablyinfiltrated into the recess of each lead, whereby the bonding strengthbetween each lead and the resin package can be reliably improved.

Preferably, the area of the recess in bottom plan view is not more thanhalf the total area of the lower surface of the lead. With such a sizeof the recess, the bonding wire can be bonded to a relatively thickportion of the lead, while improvement in bonding strength between thelead and the resin package can be attained. Further, a contact area ofthe lead with respect to a wiring board can be sufficiently ensured.

Preferably, the lead has a side surface exposed on a side surface of theresin package, and a portion of the lead along the exposed side surfaceis provided with a recessed groove concaved from the lower surface sideof the lead over the total width in a direction along the side surface.The material for the resin package also infiltrates into the recessedgroove, whereby further improvement in bonding strength between the leadand the resin package can be attained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a bottom plan view of a semiconductor device according to afirst embodiment of the present invention.

FIG. 2 is a schematic sectional view of the semiconductor device shownin FIG. 1 taken along a cutting plane line II-II.

FIG. 3 is a bottom plan view of a semiconductor device according to asecond embodiment of the present invention.

FIG. 4 is a bottom plan view of a semiconductor device according to athird embodiment of the present invention.

FIG. 5 is a bottom plan view of a semiconductor device according to afourth embodiment of the present invention.

FIG. 6 is a bottom plan view of a semiconductor device according to afifth embodiment of the present invention.

FIG. 7 is a bottom plan view of a semiconductor device according to asixth embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are now described in detail withreference to the attached drawings.

FIG. 1 is a bottom plan view of a semiconductor device according to afirst embodiment of the present invention. FIG. 2 is a schematicsectional view of the semiconductor device shown in FIG. 1 taken along acutting plane line II-II.

A semiconductor device 1 has a structure obtained by sealing asemiconductor chip 2 with a resin package 4 along with a lead frame 3.The contour of the semiconductor device 1 is in the shape of a flatrectangular parallelepiped (a hexahedron square-shaped in plan viewaccording to the embodiment).

The lead frame 3 is formed by punching a thin metal plate (a thin copperplate, for example), and includes an island 5 and four leads 6 arrangedaround the island 5.

The island 5 is quadrangularly shaped in plan view (square-shaped inplan view according to the embodiment). The lower surface of the island5 is exposed on the rear surface of the resin package 4.

The leads 6 are arranged on portions opposed to the four sides of theisland 5 respectively in bottom plan view. Each lead 6 is trapezoidallyshaped in bottom plan view. More specifically, each lead 6 is providedin a shape having a side 7 parallel to the opposed side of the island 5,aside 8 extending on a side surface of the resin package 4, a side 9orthogonal to the side 8 and extending parallelly to another sidesurface of the resin package 4, and sides 10 and 11 connecting the side7 with the sides 8 and 9 respectively in plan view.

Each lead 6 is provided with a recess 12, semicircularly shaped inbottom plan view, concaved from the side of the lower surface (theexposed surface) of the lead 6 and opened on a side surface opposed tothe island 5, i.e., the side surface having the side 7. The material forthe resin package 4 infiltrates into the recess 12. The recess 12 can beformed by chemical etching or crushing, for example.

The lower surface of each lead 6 is exposed on the rear surface of theresin package 4 except the recess 12, to function as an externalterminal for connection with a wiring board (not shown). The sidesurface of each lead 6 having the side 8 is exposed on the correspondingside surface of the resin package 4.

The rear surface of the semiconductor chip 2 is bonded (die-bonded) tothe island 5 through a conductive bonding agent, in a state upwardlydirecting a surface (a device forming surface) on a side provided withfunctional elements. On the surface of the semiconductor chip 2, a pad(not shown) is formed by exposing part of a wiring layer from a surfaceprotective film, correspondingly to each lead 6. An end of a bondingwire 13 is bonded to each pad. Another end of the bonding wire 13 isbonded to the upper surface of a relatively thick portion (a portion notprovided with the recess 12) in each lead 6. Thus, the semiconductorchip 2 is electrically connected with the lead 6 through the bondingwire 13.

As hereinabove described, the lower surfaces of the island 5 and theleads 6 are exposed on the rear surface of the resin package 4.Therefore, the semiconductor device 1 is surface-mountable on the wiringboard.

Each lead 6 is provided with the recess 12 concaved from the lowersurface side thereof and opened on the side surface having the side 7.The material for the resin package 4 infiltrates into the recess 12,whereby the portion of each lead 6 provided with the recess 12 is heldby the resin package 4 from both of the upper and lower sides thereof.Thus, improvement in bonding strength between each lead 6 and the resinpackage 4 can be attained. Consequently, the lead 6 can be preventedfrom coming off the resin package 4.

The recess 12 is opened on the side surface having the side 7, wherebythe material for the resin package 4 can be reliably infiltrated intothe recess 12.

Further, the recess 12 is semicircularly shaped in bottom plan view,whereby the bonding strength between the lead 6 and the resin package 4in all radial directions of the arc thereof can be increased.

FIG. 3 is a bottom plan view of a semiconductor device according to asecond embodiment of the present invention. Referring to FIG. 3,portions corresponding to those shown in FIG. 1 are denoted by the samereference signs as those assigned to the portions. In the following,only a point different from the structure shown in FIG. 1 is describedas to the structure shown in FIG. 3, and description of the portionsdenoted by the same reference signs is omitted.

In a semiconductor device 31 shown in FIG. 3, each lead 6 is providedwith a recess 32, right-triangularly shaped in bottom plan view,concaved from the lower surface side thereof and opened on a sidesurface having a side 7. The material for a resin package 4 infiltratesinto the recess 32. The recess 32 can be formed by chemical etching orcrushing, for example.

Also in this structure, improvement in bonding strength between eachlead 6 and the resin package 4 can be attained. Consequently, the lead 6can be prevented from coming off the resin package 4.

FIG. 4 is a bottom plan view of a semiconductor device according to athird embodiment of the present invention. Referring to FIG. 4, portionscorresponding to those shown in FIG. 1 are denoted by the same referencesigns as those assigned to the portions. In the following, only a pointdifferent from the structure shown in FIG. 1 is described as to thestructure shown in FIG. 4, and description of the portions denoted bythe same reference signs is omitted.

In a semiconductor device 41 shown in FIG. 4, a portion of each lead 6having a side 8 is provided with a recessed groove 42 concaved from thelower surface side of each lead 6 over the total width in a directionalong the side 8.

According to this structure, the material for a resin package 4infiltrates into a recess 12 and the recessed groove 42, whereby furtherimprovement in bonding strength between each lead 6 and the resinpackage 4 can be attained.

FIG. 5 is a bottom plan view of a semiconductor device according to afourth embodiment of the present invention. Referring to FIG. 5,portions corresponding to those shown in FIG. 1 are denoted by the samereference signs as those assigned to the portions. In the following,only a point different from the structure shown in FIG. 1 is describedas to the structure shown in FIG. 5, and description of the portionsdenoted by the same reference signs is omitted.

In a semiconductor device 51 shown in FIG. 5, each lead 6 is providedwith recesses 12, 52 and 53, semicircularly shaped in bottom plan view,concaved from the lower surface side thereof and opened on side surfaceshaving sides 7, 8 and 9 respectively.

According to this structure, the material for a resin package 4infiltrates into the recesses 12, 52 and 53, whereby further improvementin bonding strength between each lead 6 and the resin package 4 can beattained.

FIG. 6 is a bottom plan view of a semiconductor device according to afifth embodiment of the present invention. Referring to FIG. 6, portionscorresponding to those shown in FIG. 1 are denoted by the same referencesigns as those assigned to the portions. In the following, only a pointdifferent from the structure shown in FIG. 1 is described as to thestructure shown in FIG. 6, and description of the portions denoted bythe same reference signs is omitted.

In a semiconductor device 61 shown in FIG. 6, each lead 6 is providedwith a recess 62, semicircularly shaped in bottom plan view, having asize larger than that of the recess 12 shown in FIG. 1. The recess 62 isconcaved from the lower surface side thereof, and opened on a sidesurface having a side 7. The area of the recess 62 in bottom plan viewis about half the total area of the lower surface of the lead 6.

When the area of the recess 62 in bottom plan view is not more than halfthe total area of the lower surface of the lead 6, a bonding wire 13 canbe bonded to a relatively thick portion of the lead 6, while improvementin bonding strength between the lead 6 and a resin package 4 can beattained. Further, a contact area of the lead 6 with respect to a wiringboard can be sufficiently ensured.

FIG. 7 is a bottom plan view of a semiconductor device according to asixth embodiment of the present invention. Referring to FIG. 7, portionscorresponding to those shown in FIG. 1 are denoted by the same referencesigns as those assigned to the portions. In the following, only a pointdifferent from the structure shown in FIG. 1 is described as to thestructure shown in FIG. 7, and description of the portions denoted bythe same reference signs is omitted.

In a semiconductor device 71 shown in FIG. 7, an island 5 is providedwith groovelike recesses 62 concaved from the lower surface side thereofand extending along two diagonal lines of the island 5 in bottom planview. The material for a resin package 4 infiltrates into the recesses72. The recesses 72 can be formed by chemical etching or crushing, forexample.

The material for the resin package 4 infiltrates into the recesses 72,whereby portions of the island 5 provided with the recesses 72 are heldby the resin package 4 from both of the upper and lower sides thereof.Thus, improvement in bonding strength between the island 5 and the resinpackage 4 can be attained. Consequently, the island 5 can be preventedfrom coming off the resin package 4.

While the first to sixth embodiments of the present invention have beendescribed, the first to sixth embodiments may be properly combined andexecuted. For example, the first embodiment and the fourth embodimentmay be so combined that one or two of the three recesses 12, 52 and 53shown in FIG. 5 are semicircularly shaped in bottom plan view and therest is right-triangularly shaped in bottom plan view. Further, thesecond embodiment and the third embodiment may be so combined that eachlead 6 is provided with the recess 32 right-triangularly shaped inbottom plan view shown in FIG. 3 and the recessed groove 42 shown inFIG. 4.

While the present invention has been described in detail by way of theembodiments thereof, it should be understood that these embodiments aremerely illustrative of the technical principles of the present inventionbut not limitative of the invention. The spirit and scope of the presentinvention are to be limited only by the appended claims.

1. A semiconductor device comprising: a semiconductor chip; an islandhaving an upper surface to which the semiconductor chip is bonded; aplurality of leads arranged around the island; a bonding wire extendingbetween the surface of the semiconductor chip and the upper surface ofthe lead; and a resin package collectively sealing the semiconductorchip, the island, the leads and the bonding wire; wherein the lowersurface of the island and the lower surface of the leads are exposed onthe rear surface of the resin package, wherein the island has an areadefined by four sides, each of which is not facing any sides of theresin package, in bottom plan view; wherein the leads are arranged oncorners of the semiconductor device in bottom plan view, respectively;wherein each of the leads has a side facing the side of the island;wherein the semiconductor device further comprises a facing portionincluding the side of the island and the side of the lead facing eachother; and wherein the facing portion has an etched portion keeping theside of the island and the side of the lead selectively non-parallel. 2.The semiconductor device according to claim 1, wherein the etchedportion is formed at a position apart from a corner of at least one ofthe leads.
 3. The semiconductor device according to claim 1, wherein theetched portion is arcuately shaped in bottom plan view.
 4. Thesemiconductor device according to claim 1, wherein the etched portionincludes a coming-off preventing portion below which a part of the resinpackage infiltrates in sectional plan view.
 5. The semiconductor deviceaccording to claim 4, wherein the coming-off preventing portion has aportion parallel to a lower surface of the semiconductor device.
 6. Thesemiconductor device according to claim 4, wherein the coming-offpreventing portion is held by the resin package from both of the upperand lower sides thereof.
 7. The semiconductor device according to claim4, wherein the coming-off preventing portion further covers the part ofthe resin package from a side thereof.
 8. The semiconductor deviceaccording to claim 1, wherein the etched portion is disposed at a centerof the facing portion.
 9. The semiconductor device according to claim 1,wherein both the side of the island and the side of at least one of theleads have a liner portion inclined with respect to a side of the resinpackage in bottom plan view.
 10. A semiconductor device comprising: asemiconductor chip; an island having an upper surface, the semiconductorchip being bonded to the upper surface of the island; at least one leaddisposed around the island; a bonding wire extending between the surfaceof the semiconductor chip and the upper surface of the at least onelead; and a resin package sealing the semiconductor chip, the island,the at least one lead, and the bonding wire; wherein the lower surfaceof the island and the lower surface of the at least one lead are exposedon the rear surface of the resin package; wherein the island has foursides, each of the four sides of the island not facing any side of theresin package, in bottom plan view; wherein the at least one lead isdisposed on a corner of the semiconductor device in bottom plan view;wherein the at least one lead has a side facing one or more sides of theisland; wherein at least one side of the island and at least one side ofthe at least one lead face each other and form a facing portion; andwherein the facing portion has an etched portion, the etched portionmaking the at least one side of the island and the at least one side ofthe at least one lead non-parallel.
 11. The semiconductor deviceaccording to claim 10, wherein the etched portion is formed at aposition apart from a corner of the at least one lead.
 12. Thesemiconductor device according to claim 10, wherein the etched portionis arcuately shaped in bottom plan view.
 13. The semiconductor deviceaccording to claim 10, wherein the etched portion includes a coming-offpreventing portion below which a part of the resin package infiltratesin sectional plan view.
 14. The semiconductor device according to claim13, wherein the coming-off preventing portion has a portion parallel toa lower surface of the semiconductor device.
 15. The semiconductordevice according to claim 13, wherein the coming-off preventing portionis held by the resin package from both of the upper and lower sidesthereof.
 16. The semiconductor device according to claim 13, wherein thecoming-off preventing portion further covers the part of the resinpackage from a side thereof.
 17. The semiconductor device according toclaim 10, wherein the etched portion is disposed at a center of thefacing portion.
 18. The semiconductor device according to claim 10,wherein both the side of the island and the side of the at least onelead have a liner portion inclined with respect to a side of the resinpackage in bottom plan view.